US 3288379 A
Description (OCR text may contain errors)
Nov. 29, 1966 B. H. CROFT ETAL 3,283,379
FUEL INJECTION VALVES Filed Sept. 8, 1964 2 Sheets-Sheet 1 Inventors 5. h. Croff. A. Abboif Inventors fl/fiCrafi A. Abbott m w 2 n a\\\ 3 b J" LM Attorneys B. H. CROFT ETAL FUEL INJECTION VALVES 2 SheetsSheet Nov. 29, 1966 Filed Sept. 8, 1964 United States Patent 3,288,379 FUEL INJECTION VALVES Brian Hugh Croft and Adrian Abbott, Leamington Spa, England, assignors to Associated Engineering Limited, Leamington Spa, England, a British company Filed Sept. 8, 1964, Ser. No. 394,823 Claims priority, application Great Britain, Sept. 9, 1963, 35,495/ 63 2 Claims. (Cl. 239585) The present invention relates to fuel injection valves for internal combustion engines.
More particularly the invention relates to electromagnetically operated fuel injection valves in which the energisation of a solenoid is employed to control the opening of the valve to allow it to pass fuel through one or more outlet ports or orifices.
In order that the quantity of fuel passed through a solenoid operated fuel injection valve is controlled by the time duration of the energising pulse applied to the solenoid and is not dependent on voltage variations in the supply to the solenoid, it is necessary that the delay period between the beginning of an energising pulse and the movement of the valve be as small .as possible. This delay can be decreased by either reducing the force required to move the valve or by increasing the rate of rise of force from the solenoid. These two factors are in fact interlinked since any reduction in the operating force required to move the valve enables a smaller solenoid to be employed having a smaller inductance.
The present invention accordingly consists in an electromagnetically operated fuel injection valve in which the energisation of a solenoid is employed to control the opening of the valve wherein means are provided for reducing the force required to move the valve to its open position and hence reduce the time taken for the force to rise to the required value to open the valve.
The fuel injection valve may be a pressure balanced valve or may be servo operated by means of a solenoid controlled servo valve.
In order that the invention may be more fully understood, some embodiments thereof will now be described with reference to the accompanying drawings, in which FIGURE 1 is a sectional view through one embodiment of fuel injection valve according to this invention, which is a pressure balanced valve,
FIGURE 2 is a diagrammatic representation of an embodiment of servo operated fuel injection valve,
FIGURE 3 is a diagrammatic representation of a further embodiment of servo operated fuel injection valve, and
FIGURE 4 is a diagrammatic representation of a plurality of servo operated fuel injection valves which are controlled by a common servo solenoid.
FIGURE 1 is a diagram of an embodiment of fuel injection valve, which is a pressure balanced valve. Previously proposed constructions of solenoid operated fuel injection valves are not pressure balanced, so that when the tip of the valve stem is located on its seating the fuel pressure loads the valve in addition to the spring which acts to hold the valve closed. The force developed by the solenoid to attract the valve stem and open the valve must therefore be high enough to overcome the fuel pressure as well as the spring pressure and comparatively high energising currents are required by the solenoid to provide the desired magnetic attraction.
According to the present embodiment, a fuel injection valve comprises a valve body 1 within which is located a hollow valve stem 2. The valve stem comprises a lower portion 2a of a non-magnetic material such as aluminium and an upper portion 2b of magnetic material such as Swedish iron. A solenoid assembly 3 consisting of a coil wound on an iron core is mounted at the upper end of the valve body by means of the screw connection 4. An external screw thread 5 is provided on the valve body by means of which it may be screwed into a cavity in a part of an engine. A flexible diaphragm 6 is located between the valve body and the valve stem. Its outer periphery is clamped by a retaining ring 7 and its inner periphery is clamped between the parts 211 and 2b of the valve stem. The mean diameter of the effective area of the diaphragm is equal to the diameter of the line of contact of the lower tip of the valve stem and its seat, indicated at 8, whereby the forces resulting from fuel pressure are balanced whether the valve is open or closed. The tip of the valve stem seats on a member 9 provided with outlet ports 10. An annular spring 12 of nonmagnetic material arranged at the upper enlarged end 2c of the valve stem acts to hold the tip of the valve stem on its seating.
When the valve is closed, fuel at pump pressure fed through inlet 11 is present around the head 20 of the valve above the diaphragm 6 and down the central passage 13 of the valve stem to the valve seating 8. Outside the seating and on the underside of the diaphragm 6, the fuel is at inlet manifold pressure. Since the effective area of the diaphragm is chosen so that the forces on the valve are balanced, the solenoid 3 only has to overcome the force of spring 12 to open the valve. When the valve is opened, by energisation of the solenoid, the forces are again balanced and the closing of the valve is controlled by the spring 12. Therefore with a given delay period between the beginning of a pulse of solenoid energising current and the movement of the valve, the valve will operate with a considerably lower solenoid energising current than with valves where the pressure equalising diaphragm is not provided. Conversely with a higher value of solenoid energising current, the delay period between the beginning of a pulse of energising current and the movement of the valve is reduced.
FIGURE 2 is a diagrammatic representation of an embodiment of servo operated fuel injection valve. The valve consists of a piston 21 having two parts 21a and 21b of different diameters; the diameter of the upper part 21a being greater than the diameter of the lower part 2111. This piston is located in a bore 22 provided in the valve body and having two diameters to match the diameters of the two parts of the piston. The lower part of the bore is closed and is provided with an outlet orifice 23 in the centre of its end face, this orifice being closed by the tip of the piston when in its lower position. The upper part of the bore is also closed and is provided with two passages 24 and 25. The passage 24 is a fuel inlet passage and contains a small orifice 26. The other passage 25 leads to a fuel outlet passage and is several times larger than the orifice 26 in the inlet passage. The passage 25 is normally closed by a spring loaded armature 27 which can be attracted upon energisation of the solenoid 28 to open the passage. Fuel is fed under pressure through both of inlets 29 and 30 to the passage 24 and the valve seating respectively.
When the armature 27 closes the passage 25, the piston 21 is exposed to fuel pressure on both its upper and lower parts 21a and 21b. Since the area of the upper part 21a of the piston is greater than that of the lower part 2111, the valve is forced into a position in which the orifice 23 is closed. When the solenoid 28 is energized so that it attracts the armature 27, the fuel fed through passage 24 is allowed to escape through outlet passage 25 to outlet 31. Under these conditions, the greatest pressure drop between inlet 29 and outlet 31 is across orifice 26, and the pressure on the upper part 21a of the piston is substantially that of the outlet passage 31. The fuel pressure through inlet 30 acting on the bottom part 21b of the piston now produces a force which is sufficient to raise the piston and thus allow the fuel to be ejected through the orifice 23. Any fuel leaking past either end of the piston is returned to the tank through the outlet 32. Alternatively, one or more diaphragms can be provided between the piston and the valve body to prevent leakage of fuel past the piston. With this construction only a very low current is required to energise the solenoid 28 since this only has to attract the armature 27.
FIGURE 3 is a somewhat diagrammatic representation of another embodiment of fuel injection valve which is of the servo-assisted type. The valve comprises a body 41 containing a valve stem 42 having an enlarged upper end 42a which is a close sliding fit within the bore of the valve body, and a lower end 42b which can close over an outlet orifice 43 through which fuel can be ejected. The upper part of the valve body contains a servo valve 44 operated by solenoid 45. A spring 47 is located within the valve stem and urges the valve stem into the closed position. Fuel a-t pump pressure is fed through the inlets 48 and 49 simultaneously to the valve seating and the servo valve. When the solenoid 45 is de-energised, the valve is unbalanced hydraulically and a force is present due to the fuel pressure acting over the area A1 of the seat, defined by the lower end 4211 of the stem, which is less than the area A2 of the enlarged upper end 420, which assists the spring 47 to hold the valve closed. On energising the soelnoid 45 the servo valve 44 moves to close off the fuel inlet 48 and open the fuel outlet 50. The valve stem 42 will now move off its seating due to the fuel at inlet pressure acting on the underside of the enlarged upper end 42a to open the outlet orifice 43 provided that the difference between areas A1 and A2 is sufficiently great. When the solenoid is de-energised, the servo valve 44 closes olf the fuel outlet 50 and the fuel pump pressure is now reapplied to the upper enlarged end of the valve through inlet 48. The pressures on the valve stem are now balanced but the springs 47 produce a relatively small force sufficient to close the valve. The use of fuel pressure to operate the valve stem instead of magnetic force enables the solenoid size and its current consumption to be considerably reduced.
In a multi-cylinder engine it may be desirable to operate a plurality of fuel injection valves simultaneously. This can be achieved by employing only a single solenoid controlled valve to control a number of fuel injection valves. One such arrangement is shown in FIG- URE 4, which is basically similar to the construction shown in FIGURE 2 and corresponding parts bear the same reference numerals. However in this embodiment a single solenoid control arrangement 27, 28 controls the opening and closing of three fuel injection valves V1, V2, and V3 so that the valves open simultaneously upon energisation of the solenoid. The manner of operation is similar to that described with reference to FIGURE 2.
Whilst particular embodiments have been described it will be understood that various modifications may be made without departing from the scope of this inventionv Thus, the servo operated valves as described with reference to FIGURES 2 to 4 may also incorporate a pressure balancing diaphragm as described in the embodiment of FIGURE 1.
1. A servo operated fuel injection valve, comprising a valve body, a piston having an upper part of greater diameter than the lower part and located in a bore provided in the valve body, said bore having two diameters to match the diameters of the two parts of the piston, and the lower part of said bore being provided with at least one outlet orifice closed off by the lower end of the piston when in its lower position, the upper part of said body being provided with a fuel inlet passage and a fuel outlet passage, said fuel outlet passage allowing a greater rate of flow than the fuel inlet passage, an armature for closing said fuel outlet passage, a solenoid for attracting said armature to open said outlet passage and a further fuel inlet passage leading to the lower part of said bore.
2. A valve as claimed in claim 1 wherein when the valve is closed the pressure on the upper part of the piston is greater than that on the lower part of the piston which closes the at least one outlet orifice, and when the solenoid is energised the armature is moved to open the fuel outlet passage and cause a pressure drop on the upper part of the piston, whereby the fuel acting on the bottom part of the piston produces a force which is sufiicient to raise the piston and allow the fuel to be ejected through said at least one outlet orifice.
References Cited by the Examiner UNITED STATES PATENTS 10/1943 Fuscaldo 12332 4/1959 Beck et a1 239585 6/1959 Stoll 123139.17